HDMI CEC Interface Standby Power Reduction via Timer Oscillator Control
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Solution Overview
Problem
The HDMI-CEC standard does not provide specifications for reducing energy consumption in standby mode, leading to increased power usage despite the need for compliance with energy efficiency guidelines like Energy Star.
Innovation Solution
A communication system for the HDMI interface that switches between active and standby conditions using a timer and oscillator, with different reference values for detecting transmission start bits in each mode, allowing for reduced power consumption while maintaining system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the communication interface remains activated to detect and acknowledge CEC commands, then the system can respond to control signals, but the energy consumption increases in standby mode
Solution Approach 1:
The system performs preliminary detection of the CEC bus state using a timer circuit before fully activating the communication interface. The timer continuously monitors the bus for transmission activity, and only when activity is detected does the system wake up the communication interface and oscillator to process the message. This preliminary detection action allows the system to remain in low-power standby mode while still being able to respond to commands.
Solution Approach 2:
The communication interface dynamically transitions between standby mode and active mode based on detected CEC bus activity. The system uses a timer to detect transmissions, then dynamically activates the oscillator and communication interface only when needed. This dynamic behavior allows the system to optimize power consumption by being active only during necessary communication periods rather than remaining continuously active.
2Use of energy by moving object
If the oscillator is deactivated in standby mode to reduce power consumption, then energy consumption decreases, but the ability to detect transmission start bits is compromised
Solution Approach 1:
The timer circuit performs preliminary detection of transmission start bits on the CEC bus even when the oscillator is deactivated. The timer monitors the differential voltage on the CEC lines and detects the characteristic voltage transition of a start bit. When a start bit is detected, the timer triggers the oscillator to activate, ensuring that the communication interface is ready to process the incoming message without missing the start bit detection.
Solution Approach 2:
The timer circuit acts as an intermediary between the deactivated communication interface and the CEC bus. It continuously monitors the bus for transmission activity using minimal power, and when activity is detected, it triggers the oscillator and communication interface to activate. This intermediary approach allows the system to detect transmissions accurately without requiring the full communication interface to remain active, thus reducing power consumption while maintaining detection capability.
3Measurement precision
If different reference values are used for start bit detection in active and standby modes, then detection accuracy is maintained across both modes, but the system complexity increases
Solution Approach 1:
The system applies different reference values locally for start bit detection depending on the operational mode. In standby mode, the timer uses a first reference value optimized for detecting start bits when the oscillator is deactivated. In active mode, the timer uses a second reference value optimized for normal operation. This local quality approach allows the system to optimize detection accuracy for each mode without requiring a single complex detection mechanism, thereby managing system complexity effectively.
Solution Approach 2:
The system changes the reference value parameter used for start bit detection based on the operational mode. When transitioning from standby to active mode, the reference value changes from the first reference value to the second reference value. This parameter change allows the system to adapt the detection threshold to the specific conditions of each mode, maintaining high detection accuracy while using simple, mode-specific reference values rather than a complex adaptive system.
Data Source
AI summary
A communication system for an HDMI communication interface CEC channel includes a communication module for receiving messages via the CEC channel, a processing unit for processing the received messages and an oscillator for driving the communication module. When the interface is in an active mode, the system is operative to activate the timer upon detection of the start of transmission of a first message, detect the initial bit of the first message, reconstruct and process the first message, and switch the interface from the active mode to standby by deactivating the oscillator. When the interface is in standby, the system is operative to switch the interface to the active condition by activating the oscillator and the timer when the start of a transmission of a second message is detected, detect the initial bit of a transmission of the second message, and reconstruct and process the second message.